The goal is to prepare radiolabeled tumor-specific antibodies and to determine if these antibodies localize preferentially in tumors and metastatic tissue in animals. Tumor-specific antibody localization will be explored in BALB/c mice bearing syngeneic SV40 DNA virus-transformed tumors (SVT2). Irradiated cells in Freund's adjuvant will be injected at weekly intervals and sera collected one week after the last immunization, or viable SVT2 cells will be inoculated in the footpad and sera collected from animals with progressively growing tumors at six weeks. Groups of immunized and non-immunized mice will be inoculated with SVT2 and several other tumors of BALB/c mice to test the strength and specificity of the immune reaction. Sera from mice immunized with SVT2 will be tested for tumor-specific antibody activity using the isotopic antiglobulin technique developed by Harder and McKhann. The gamma globulin will be separated from the serum by ammonium sulfate precipitation and this material labeled with 125I. Normal gamma globulin will be labeled with 131I and used as a paired label control. Purification of the labeled antibodies will be by absorption and elution from the syngeneic SVT2 tumor cells; the cell bound antibody will be eluted in glycine acid buffer and dialyzed. Labeled normal gamma globulin will be freed of antibody aggregates by passage through normal BALB/c mice or Sephadex G-200 passage. In vitro binding specificity will be tested by absorption to syngeneic tumor cells and normal cells and by radioimmunoelectrophoresis using 131I-labeled rabbit or goat IgG antimouse gamma globulin fractions. In vivo localization of the labeled materials will be evaluated by tissue sampling and using a well-counter for determining radiolabel content. Labeled tumor-specific antibodies will also be produced for spontaneous tumors in cats with lymphoma. The animals will be immunized after tumor excision with weekly inoculations of inactivated tumor cells. Sera will be tested for tumor-specific antibody activity, then purified and radioiodinated, and assayed for in vitro binding specificity. The in vivo distribution of paired labeled antibody and normal gamma globulin will be studied by external scintigraphic imaging and emission CT imaging or by tissue sampling in cats with advanced tumors of the same and different histological types and the extent of the tumors will be studied at necropsy following death of the animals.